Measurement of tissue viability

ABSTRACT

The present disclosure provides apparatuses and methods for measuring sub-epidermal moisture as an indication of tissue viability and providing information regarding the location of a boundary of non-viable tissue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 15/887,837filed Feb. 2, 2018, which claims the benefit of priority of U.S.Provisional Application 62/454,487 filed Feb. 3, 2017, and U.S.Provisional Application 62/521,926 filed Jun. 19, 2017, each of which isherein incorporated by reference in its entirety.

FIELD

The present disclosure provides apparatus and methods for measuring typeand degree of tissue damage around a burn or other type of wound.

BACKGROUND

Serious wounds and burns may have regions of various degrees of damagesurrounding the wound site. Effective treatment may require removal ofnon-viable tissue, yet it can be difficult to visually assess tissueviability. For an open wound such as a burn, there may be a region ofnon-viable tissue around the immediate wound while further away thetissue may be less damaged and characterized by swelling known as“edema” yet viable and likely to recover.

A common method of burn evaluation assesses the visual and tactilecharacteristics, namely wound appearance, capillary blanching andrefill, capillary staining, and burn wound sensibility to light touchand pinprick. Estimation of the burn depth is difficult. In addition,burn wounds are dynamic and can progress over time and the changes donot immediately become visually apparent.

SUMMARY

In an aspect, the present disclosure provides for, and includes, anapparatus for mapping areas of damage around a wound, the apparatuscomprising: a plurality of electrodes embedded on a substrate configuredto be placed over an area of tissue that includes the wound, wherecombinations of the electrodes are capable of forming a plurality ofvirtual capacitive sensors and each of the virtual capacitive sensors isconfigured to measure a capacitance of a region of tissue proximate tothe respective virtual capacitive sensor, a plurality of visualindicators embedded on the substrate, a drive circuit electronicallycoupled to the electrodes and visual indicators, a processorelectronically coupled to the drive circuit, and a non-transitorycomputer-readable medium electronically coupled to the processor andcomprising instructions stored thereon that, when executed on theprocessor, perform the steps of: receiving information regarding themeasured capacitance from a subset of the plurality of virtualcapacitive sensors via the drive circuit, determining a boundary betweenviable and non-viable tissue, and activating via the drive circuit aportion of the plurality of visual indicators to indicate the boundary.

In an aspect, the present disclosure provides for, and includes, anapparatus for determining a depth of a burn wound, the apparatuscomprising: a pair of electrodes capable of forming a capacitive sensorthat is configured to measure a capacitance of a region of tissueproximate to the pair of electrodes, a drive circuit electronicallycoupled to the capacitive sensor, a processor electronically coupled tothe drive circuit, and a non-transitory computer-readable mediumelectronically coupled to the processor and comprising instructionsstored thereon that, when executed on the processor, perform the stepsof: receiving information regarding the measured capacitance from thecapacitive sensor via the drive circuit, comparing the information to adata array comprising pairs of capacitances and depths of burns, anddetermining the depth of the burn wound associated with the measuredcapacitance.

In an aspect, the present disclosure provides for, and includes, anapparatus for mapping areas of damage around a wound, the apparatuscomprising: a plurality of electrodes embedded on a substrate configuredto be placed over a portion of an area of tissue that includes thewound, where pairs of the electrodes are capable of forming a capacitivesensor that is configured to measure a capacitance of a region of tissueproximate to the capacitive sensor, a projector capable of projecting avisual indicator onto the area of tissue that includes the wound, adrive circuit electronically coupled to the plurality of electrodes andthe projector, a processor electronically coupled to the drive circuit,and a non-transitory computer-readable medium electronically coupled tothe processor and comprising instructions stored thereon that, whenexecuted on the processor, perform the steps of: receiving informationregarding the measured capacitance from one or more of the formedcapacitive sensors, determining a first boundary between a first type oftissue and a second type of tissue, and causing the projector to projectthe visual indicator to indicate the boundary.

In one aspect, the present disclosure provides for, and includes amethod for mapping areas of damage around a wound, the methodcomprising: obtaining capacitance measurements over an area of a tissueincluding the wound using a plurality of electrodes; converting eachmeasured capacitance to an associated sub-epidermal moisture (SEM)value; and marking a first boundary encompassing regions of tissueassociated with SEM values that are lesser than a first threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

Some aspects of the disclosure are herein described, by way of exampleonly, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and are for purposes ofillustrative discussion of aspects of the disclosure. In this regard,the description and the drawings, considered alone and together, makeapparent to those skilled in the art how aspects of the disclosure maybe practiced.

FIG. 1A discloses a toroidal bioimpedance sensor.

FIG. 1B discloses an idealized field map created by the toroidal sensorof FIG. 1A when activated.

FIG. 1C discloses a SEM scanner that comprises the sensor of FIG. 1A.

FIG. 2 is a first exemplary array of electrodes.

FIG. 3 is an exemplary array of electrodes according to the presentdisclosure.

FIG. 4A illustrates a first example of how the array of electrodesdisclosed in FIG. 3 is configured to form a bioimpedance sensoraccording to the present disclosure.

FIG. 4B illustrates a second example of how the array of electrodesdisclosed in FIG. 3 is configured to form a bioimpedance sensoraccording to the present disclosure.

FIG. 5A depicts an example 3^(rd)-degree burn with an open wound.

FIG. 5B depicts a cross-section of the wound of FIG. 5A.

FIG. 6 provides an example plot 600 of how SEM values may vary acrossthe wound of FIG. 5A, according to the present disclosure.

FIG. 7 discloses a first exemplary aspect of an SEM sensing apparatusaccording to the present disclosure.

FIG. 8A discloses a second exemplary aspect of an SEM sensing apparatusaccording to the present disclosure.

FIG. 8B discloses a third exemplary aspect of an SEM sensing apparatusaccording to the present disclosure.

FIG. 9 discloses an aspect of an apparatus for mapping areas of damageaccording to the present disclosure.

DETAILED DESCRIPTION

The present disclosure describes measurement of various electricalcharacteristics and derivation of SEM values indicative of theaccumulation or depletion of extracellular fluid (ECF), also referred toas intercellular fluid, and the application of this information to theassessment of tissue viability. Examples are provided of application tothermal burns yet are applicable to other types of wounds. Theseexamples are not limiting and the demonstrated principles may be appliedto a larger scope of injuries and conditions than the specific example.For example, apparatus and methods disclosed in relation to a3^(rd)-degree burn may be used with equal efficacy to an open cut,gangrene, an ulcer, or other similar injury.

Assessment of tissue viability around wounds and burns may be improvedby determination of the amount of SEM in the tissue surrounding theactual damage. Typically, the tissue immediately around a wound willexhibit a reduced level of SEM, indicating a lower level of tissueviability. Further out from the wound, the tissue will exhibit anincreased level of moisture, or edema. This value may be very higharound the edge of the low-moisture tissue, indicating a high degree ofdamage with a high risk of eventual tissue death. The SEM value maytaper off with increasing distance from the wound, where a moderatelyraised SEM level indicates damage with a higher chance of tissueviability. Mapping the areas of low-viability tissue, as indicated byreduced levels of tissue moisture, and the surrounding area of edema canprovide important guidance to a clinician during the treatment of thewound.

This description is not intended to be a detailed catalog of all thedifferent ways in which the disclosure may be implemented, or all thefeatures that may be added to the instant disclosure. For example,features illustrated with respect to one embodiment may be incorporatedinto other embodiments, and features illustrated with respect to aparticular embodiment may be deleted from that embodiment. Thus, thedisclosure contemplates that in some embodiments of the disclosure, anyfeature or combination of features set forth herein can be excluded oromitted. In addition, numerous variations and additions to the variousembodiments suggested herein will be apparent to those skilled in theart in light of the instant disclosure, which do not depart from theinstant disclosure. In other instances, well-known structures,interfaces, and processes have not been shown in detail in order not tounnecessarily obscure the invention. It is intended that no part of thisspecification be construed to effect a disavowal of any part of the fullscope of the invention. Hence, the following descriptions are intendedto illustrate some particular embodiments of the disclosure, and not toexhaustively specify all permutations, combinations and variationsthereof.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. The terminology used in thedescription of the disclosure herein is for the purpose of describingparticular embodiments or aspects only and is not intended to belimiting of the disclosure.

All publications, patent applications, patents and other referencescited herein are incorporated by reference in their entireties for theteachings relevant to the sentence and/or paragraph in which thereference is presented. References to techniques employed herein areintended to refer to the techniques as commonly understood in the art,including variations on those techniques or substitutions of equivalenttechniques that would be apparent to one of skill in the art.

U.S. patent application Ser. Nos. 14/827,375 and 15/134,110 areincorporated herein by reference in their entirety.

Unless the context indicates otherwise, it is specifically intended thatthe various features of the disclosure described herein can be used inany combination. Moreover, the present disclosure also contemplates thatin some embodiments of the disclosure, any feature or combination offeatures set forth herein can be excluded or omitted.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of thepresent invention. In other words, unless a specific order of steps oractions is required for proper operation of the embodiment, the orderand/or use of specific steps and/or actions may be modified withoutdeparting from the scope of the present invention.

As used in the description of the disclosure and the appended claims,the singular forms “a,” “an” and “the” are intended to include theplural forms as well, unless the context clearly indicates otherwise.

As used herein, “and/or” refers to and encompasses any and all possiblecombinations of one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

The terms “about” and “approximately” as used herein when referring to ameasurable value such as a length, a frequency, or a SEM value and thelike, is meant to encompass variations of ±20%, ±10%, ±5%, ±1%, ±0.5%,or even ±0.1% of the specified amount.

As used herein, phrases such as “between X and Y” and “between about Xand Y” should be interpreted to include X and Y. As used herein, phrasessuch as “between about X and Y” mean “between about X and about Y” andphrases such as “from about X to Y” mean “from about X to about Y.”

The terms “comprise,” “comprises,” and “comprising” as used herein,specify the presence of the stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

As used herein, the transitional phrase “consisting essentially of”means that the scope of a claim is to be interpreted to encompass thespecified materials or steps recited in the claim and those that do notmaterially affect the basic and novel characteristic(s) of the claimeddisclosure. Thus, the term “consisting essentially of” when used in aclaim of this disclosure is not intended to be interpreted to beequivalent to “comprising.”

As used herein, the term “sub-epidermal moisture” or “SEM” refers to theincrease in tissue fluid and local edema caused by vascular leakinessand other changes that modify the underlying structure of the damagedtissue in the presence of continued pressure on tissue, apoptosis,necrosis, and the inflammatory process.

As used herein, a “system” may be a collection of devices in wired orwireless communication with each other.

As used herein, “interrogate” refers to the use of radiofrequency energyto penetrate into a patient's skin.

As used herein, a “patient” may be a human or animal subject.

As used herein, a “3^(rd)-degree burn” refers to a full thickness burnthat goes through the dermis and affect deeper tissues.

FIG. 1A discloses a toroidal bioimpedance sensor 90. In this exemplaryconfiguration, a center electrode 110 is surrounded by a ring electrode120. Without being limited to a particular theory, a gap between twoelectrodes of sensor 90 can affect the depth of field penetration into asubstrate below sensor 90. In an aspect, a ground plane (not visible inFIG. 1A), is parallel to and separate from the plane of the electrodes.In one aspect, a ground plan extends beyond the outer diameter of ringelectrode 120. Without being limited to a particular theory, a groundplane can limit the field between electrodes 110 and 120 to a singleside of the plane of electrodes 110 and 120 that is on the opposite sideof the plane of electrodes 110 and 120 from the ground plane.

FIG. 1B discloses an idealized field map created by a toroidal sensor ofFIG. 1A when activated by a drive circuit (not shown in FIG. 1B). In oneaspect, when an electric voltage is applied across two electrodes 110,120, an electric field 140 is generated between electrodes 110 and 120that extends outward from the plane of electrodes 110 and 120 to a depthof field 150. In an aspect, the diameter of a center electrode 110, theinner and outer diameters of a ring electrode 120, and the gap betweentwo electrodes 110 and 120 may be varied to change characteristics offield 140, for example the depth of field 150.

In use, a drive circuit can measure an electrical property or parameterthat comprises one or more of a resistance, a capacitance, aninductance, an impedance, a reluctance, or other electricalcharacteristic as sensed by electric field 140. Depending on the type ofdrive circuit being employed in an apparatus, a sensor of an apparatusmay be a bipolar radiofrequency sensor, a bioimpedance sensor, acapacitive sensor, or an SEM sensor. In an aspect, the measuredelectrical parameter is related to the moisture content of the epidermisof a patient at a depth that is determined by the geometry of electrodes110 and 120, the frequency and strength of electrical field 140, andother operating characteristics of an apparatus drive circuit. In oneaspect, the measured moisture content is equivalent to the SEM contentwith a value on a predetermined scale. In an aspect, a predeterminedscale may range from 0 to 20, such as from 0 to 1, from 0 to 2, from 0to 3, from 0 to 4, from 0 to 5, from 0 to 6, from 0 to 7, from 0 to 8,from 0 to 9, from 0 to 10, from 0 to 11, from 0 to 12, from 0 to 13,from 0 to 14, from 0 to 15, from 0 to 16, from 0 to 17, from 0 to 18,from 0 to 19. In one aspect, a predetermined scaled can be scaled by afactor or a multiple based on the values provided herein.

FIG. 1C provides top and bottom views of a SEM scanner 170 thatcomprises electronics that drive sensor 174, which is similar to sensor90 of FIG. 1A, and measure a capacitance between electrodes 110 and 120.This capacitance is converted to a SEM value that is displayed ondisplay 176.

These aspects of sensor 90 and SEM scanner 170 are disclosed in WO2016/172263, from which the U.S. patent application Ser. No. 15/134,110was filed as a national phase entry.

FIG. 2 depicts an exemplary electrode array 290, according to thepresent disclosure. In an aspect, an array 290 is composed of individualelectrodes 300 disposed, in this example, in a regular pattern over asubstrate 292. In an aspect, each electrode 300 is separately coupled(through conductive elements not shown in FIGS. 2 through 4B) to acircuit, such as described with respect to FIG. 4A, that is configuredto measure an electrical parameter. In one aspect, a “virtual sensor” iscreated by selective connection of predetermined subsets of electrodes300 to a common element of a circuit. In one aspect, a particularelectrode 310 is connected as a center electrode, similar to electrode110 of FIG. 1A, and six electrodes 320A-320F are connected together as a“virtual ring” electrode, similar to electrode 120 of FIG. 1A. In anaspect, two individual electrodes are individually connected to acircuit to form a virtual sensor, for example electrodes 310 and 320Aare respectively connected as two electrodes of a sensor. In one aspect,one or more electrodes 300 are connected together to form one or theother electrodes of a two-electrode sensor.

Any pair of electrodes, whether composed of single electrodes or a setof electrodes coupled together to form virtual electrodes, is coupled toelectronics that are configured to measures an electrical property orparameter that comprises one or more of a resistance, a capacitance, aninductance, an impedance, a reluctance, or other electricalcharacteristic with one or more of sensors 90, 174, 290, 430, 440, orother two-electrode sensor.

FIG. 3 depicts another exemplary array 400 of electrodes 410, accordingto the present disclosure. In an aspect, each of electrodes 410 is anapproximate hexagon that is separated from each of the surroundingelectrodes 410 by a gap 420. In one aspect, electrodes 410 are one ofcircles, squares, pentagons, or other regular or irregular shapes. In anaspect, gap 420 is uniform between all electrodes 410. In one aspect,gap 420 varies between various electrodes. In an aspect, electrodes 410may be interconnected to form virtual sensors as described below withrespect to FIGS. 5A and 5B.

FIG. 4A depicts an array 400 of electrodes 410 that are configured, e.g.connected to a measurement circuit, to form a sensor 430, according tothe present disclosure. In an aspect, a single hexagonal electrode 410that is labeled with a “1” forms a center electrode and a ring ofelectrodes 410 that are marked with a “2” are interconnected to form aring electrode. In an aspect, electrodes 410 between the center and ringelectrode are electrically “floating.” In one aspect, electrodes 410between the center and ring electrode are grounded or connected to afloating ground. In one aspect, electrodes 410 that are outside the ringelectrode are electrically “floating.” In an aspect, electrodes 410 thatare outside the virtual ring electrode are grounded or connected to afloating ground.

FIG. 4B depicts an alternate aspect where an array 400 of electrodes 410has been configured to form a virtual sensor 440, according to thepresent disclosure. In an aspect, multiple electrodes 410, indicated bya “1,” are interconnected to form a center electrode while a double-widering of electrodes, indicated by a “2,” are interconnected to form aring electrode. In one aspect, various numbers and positions ofelectrodes 410 are interconnected to form virtual electrodes of avariety of sizes and shapes.

FIG. 5A depicts an example wound, in this case a 3^(rd)-degree burn 500with an open wound 510. Response of tissue around a 3^(rd)-degree burninjury may comprise three zones. In an aspect, innermost zone 520 at thecenter of a wound will have necrosis with no perfusion of oxygen andirreversible damage due to the coagulation of proteins. In one aspect,second zone 530, also known as the “zone of stasis,” is a ring around afirst zone 520, where there is a decrease in perfusion and a reductionin SEM. Without being limited to a particular theory, capillaries may benonfunctional in second zone 530, leading to increased permeability ofcapillaries and arterioles and subsequent ischemia reperfusion injury.There may be a chance of tissue recovery in second zone 530 if cascadingrelease of free radicals and cellular damage leading to apoptosis can beprevented. In an aspect, surrounding a second zone 530 is a zone 540 ofhyperaemia where the tissue is damaged but retains good perfusion andwill generally heal. Without being limited to a particular theory, thesize, shape, and depth of wound 510 as well as zones 520, 530, 540depends on the details of the event that caused the injury. Inaccordance with the present disclosure, evaluation of burn depth andextent is one component on which treatment decisions are based, asinaccuracies can lead to unnecessary surgeries or patients staying forextensive lengths of time.

FIG. 5B is a cross-section of a burn 500 shown in FIG. 5A, taken alongline A-A in FIG. 5A. In an aspect, a first region 520 may extend belowan open wound 510 as well as to the sides. In one aspect, a region 530may extend below one or both of an open wound 510 and region 520. In anaspect, at some distance from open wound 510, there will be undamaged,or “normal,” tissue 540.

In accordance with the present disclosure, burns may be characterized as“partial thickness” or “full thickness” burns, depending upon whetherdamaged zones 530 and 540 extend through a skin into subcutaneoustissue. Superficial partial-thickness injuries, such as a blister of a2nd-degree burn, are viable and will generally heal with antimicrobialdressings. Deep partial-thickness wounds are more like full-thicknessburns and may require surgical excision and grafting for improvedfunctional and cosmetic outcomes. Partial-thickness wounds arecomplicated to treat, as it is difficult to determine if viablestructures are present and capable of healing the wound. Whateverinaccuracies associated with diagnosis may affect treatment, as it ispossible that a superficial burn will receive surgery for a healingwound.

Burn wounds are challenging problems as they are dynamic and have thecapacity to change and progress over time. In zone 520, heating of thetissue has caused complete necrosis of the dermis and all dermalstructures along with fat necrosis. Without being limited to aparticular theory, moisture content of zone 520 is lower than normal andremains low after the injury due to destruction of the local bloodvessels, which prevents perfusion into the necrotic region.

Without being limited to a particular theory, in zone 530, return ofblood flow after the initial thermal exposure restores perfusion andoxygenation. While not being limited to theory, the restoration ofoxygenation can be important for cellular survival but also initiates acascade of events that results in production of free radicals that leadto further tissue injury. The accumulation of burn edema can occur in atwo-phase pattern. In the first phase, there is a rapid increase ininterstitial fluid within the first hour post-injury and approximately80% of total edema is present at 4 hours post-injury. The second phaseis marked by a gradual increase in fluid accumulation over the next12-24 hours. In non-burn injuries, fluid movement from the capillary tothe interstitium may be generally balanced by lymphatic clearance sothat excess fluid does not accumulate. However, in burn injuries, whilenot being limited to theory, the movement of fluid and protein into theextravascular space can occur very rapidly and edema ensues because thelymphatics are unable to keep pace with the clearance of fluid andprotein. Accordingly, again without being limited to a particulartheory, in an aspect, the amount of edema in zone 540 is less than inzone 530, although the amount of SEM is still increased above normal.Mapping the pattern of edema allows an assessment of which tissue is atrisk.

FIG. 6 depicts an example plot 600 of how SEM values may vary acrossburn 500, according to the present disclosure. SEM values taken alongcross-section A-A have been plotted as curve 610, with the x-axis beingthe location along cross-section A-A and the y-axis being the SEM value.A reference line 612 indicates normal tissue SEM value, which may astandard reference value or a measurement of known undamaged tissue onthe patient.

In an aspect, curve 610 generally shows a region 620 where a SEM valueis greater than reference line 612. In one aspect, curve 610 in region620 may be only slightly raised, as indicated by the bottom of theshaded region, or may be significantly increased as indicated by the topof the shaded region 620. In an aspect, a peak value 622 of region 620is an indication of the degree or depth of the damage in zone 530.

In one aspect, point 630 on curve 610 indicates a transition from zone530 to zone 540. In an aspect, a SEM value is higher than reference line612 but not so elevated as to indicate a risk that a tissue will notrecover. In one aspect, location of a transition from zone 530 to zone540 may be identified on curve 610 as the x-axis position of a point 630using a known magnitude of a SEM value. In an aspect, the magnitude of aSEM value at point 630 may be a value selected from the group consistingof a predetermined value, a predetermined increase above a reference SEMvalue, a percentage of a reference SEM value, a percentage of peak value622, and other value determined from curve 610.

In an aspect, a predetermined SEM value may range from 0.1 to 8.0, suchas from 0.1 to 1.0, from 1.1 to 2.0, from 2.1 to 3.0, from 3.1 to 4.0,from 4.1 to 5.0, from 5.1 to 6.0, from 6.1 to 7.0, from 7.1 to 8.0, from0.1 to 7.5, from 0.5 to 8.0, from 1.0 to 7.0, from 1.5 to 6.5, from 2.0to 6.0, from 3.0 to 5.5, from 3.5 to 5.0, or from 4.0 to 4.5. In anaspect, a predetermined SEM value may range from 0.1 to 4.0, such asfrom 0.5 to 4.0, from 0.1 to 3.5, from 1.0 to 3.5, from 1.5 to 4.0, from1.5 to 3.5, from 2.0 to 4.0, from 2.5 to 3.5, from 2.0 to 3.0, from 2.0to 2.5, or from 2.5 to 3.0. In one aspect, a predetermined SEM value mayrange from 4.1 to 8.0, such as from 4.5 to 8.0, from 4.1 to 7.5, from5.0 to 7.5, from 5.5 to 7.0, from 5.5 to 7.5, from 6.0 to 8.0, from 6.5to 7.5, from 6.0 to 7.0, from 6.0 to 6.5, or from 6.5 to 7.0. In oneaspect, a predetermined SEM value may be about 0.3, 0.35, 0.4, 0.45,0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2,1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6,2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0,4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4,5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8,6.9, 7.0, 7.1, 7.2, 7.3, 7.4, or 7.5. In an aspect, a predetermined SEMvalue can be scaled by a factor or a multiple based on the valuesprovided herein.

In an aspect, a predetermined increase may range from 0.1 to 8.0, suchas from 0.1 to 1.0, from 1.1 to 2.0, from 2.1 to 3.0, from 3.1 to 4.0,from 4.1 to 5.0, from 5.1 to 6.0, from 6.1 to 7.0, from 7.1 to 8.0, from0.1 to 7.5, from 0.5 to 8.0, from 1.0 to 7.0, from 1.5 to 6.5, from 2.0to 6.0, from 3.0 to 5.5, from 3.5 to 5.0, or from 4.0 to 4.5. In anaspect, a predetermined increase may range from 0.1 to 4.0, such as from0.5 to 4.0, from 0.1 to 3.5, from 1.0 to 3.5, from 1.5 to 4.0, from 1.5to 3.5, from 2.0 to 4.0, from 2.5 to 3.5, from 2.0 to 3.0, from 2.0 to2.5, or from 2.5 to 3.0. In one aspect, a predetermined increase mayrange from 4.1 to 8.0, such as from 4.5 to 8.0, from 4.1 to 7.5, from5.0 to 7.5, from 5.5 to 7.0, from 5.5 to 7.5, from 6.0 to 8.0, from 6.5to 7.5, from 6.0 to 7.0, from 6.0 to 6.5, or from 6.5 to 7.0. In oneaspect, a predetermined increase may be about 0.3, 0.35, 0.4, 0.45, 0.5,0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3,1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7,2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1,4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5,5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9,7.0, 7.1, 7.2, 7.3, 7.4, or 7.5. In an aspect, a predetermined increasecan be scaled by a factor or a multiple based on the values providedherein.

In one aspect, a reference SEM value is represented by a reference line612. In an aspect, a reference SEM value may range from 0.1 to 8.0, suchas from 0.1 to 1.0, from 1.1 to 2.0, from 2.1 to 3.0, from 3.1 to 4.0,from 4.1 to 5.0, from 5.1 to 6.0, from 6.1 to 7.0, from 7.1 to 8.0, from0.1 to 7.5, from 0.5 to 8.0, from 1.0 to 7.0, from 1.5 to 6.5, from 2.0to 6.0, from 3.0 to 5.5, from 3.5 to 5.0, or from 4.0 to 4.5. In anaspect, a reference SEM value may range from 0.1 to 4.0, such as from0.5 to 4.0, from 0.1 to 3.5, from 1.0 to 3.5, from 1.5 to 4.0, from 1.5to 3.5, from 2.0 to 4.0, from 2.5 to 3.5, from 2.0 to 3.0, from 2.0 to2.5, or from 2.5 to 3.0. In one aspect, a reference SEM value may rangefrom 4.1 to 8.0, such as from 4.5 to 8.0, from 4.1 to 7.5, from 5.0 to7.5, from 5.5 to 7.0, from 5.5 to 7.5, from 6.0 to 8.0, from 6.5 to 7.5,from 6.0 to 7.0, from 6.0 to 6.5, or from 6.5 to 7.0. In one aspect, areference SEM value may be about 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6,0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5,1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9,3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3,4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7,5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1,7.2, 7.3, 7.4, or 7.5. In an aspect, a reference SEM value can be scaledby a factor or a multiple based on the values provided herein.

In an aspect, a peak value may range from 0.1 to 8.0, such as from 0.1to 1.0, from 1.1 to 2.0, from 2.1 to 3.0, from 3.1 to 4.0, from 4.1 to5.0, from 5.1 to 6.0, from 6.1 to 7.0, from 7.1 to 8.0, from 0.1 to 7.5,from 0.5 to 8.0, from 1.0 to 7.0, from 1.5 to 6.5, from 2.0 to 6.0, from3.0 to 5.5, from 3.5 to 5.0, or from 4.0 to 4.5. In an aspect, a peakvalue may range from 0.1 to 4.0, such as from 0.5 to 4.0, from 0.1 to3.5, from 1.0 to 3.5, from 1.5 to 4.0, from 1.5 to 3.5, from 2.0 to 4.0,from 2.5 to 3.5, from 2.0 to 3.0, from 2.0 to 2.5, or from 2.5 to 3.0.In one aspect, a peak value may range from 4.1 to 8.0, such as from 4.5to 8.0, from 4.1 to 7.5, from 5.0 to 7.5, from 5.5 to 7.0, from 5.5 to7.5, from 6.0 to 8.0, from 6.5 to 7.5, from 6.0 to 7.0, from 6.0 to 6.5,or from 6.5 to 7.0. In one aspect, a peak value may be about 0.3, 0.35,0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0,1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4,2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8,3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2,5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6,6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, or 7.5. In an aspect, a peakvalue can be scaled by a factor or a multiple based on the valuesprovided herein.

One or more regions may be defined on a body. In an aspect, measurementsmade within a region are considered comparable to each other. A regionmay be defined as an area on the skin of the body where measurements maybe taken at any point within the area. In an aspect, a regioncorresponds to an anatomical region (e.g., heel, ankle, lower back). Inan aspect, a region may be defined as a set of two or more specificpoints relative to anatomical features where measurements are taken onlyat the specific points. In an aspect, a region may comprise a pluralityof non-contiguous areas on the body. In an aspect, the set of specificlocations may include points in multiple non-contiguous areas.

In an aspect, a region is defined by surface area. In an aspect, aregion may be, for example, between 5 and 200 cm², between 5 and 100cm², between 5 and 50 cm², or between 10 and 50 cm², between 10 and 25cm², or between 5 and 25 cm².

In an aspect, measurements may be made in a specific pattern or portionthereof. In an aspect, the pattern of readings is made in a pattern withthe target area of concern in the center. In an aspect, measurements aremade in one or more circular patterns of increasing or decreasing size,T-shaped patterns, a set of specific locations, or randomly across atissue or region. In an aspect, a pattern may be located on the body bydefining a first measurement location of the pattern with respect to ananatomical feature with the remaining measurement locations of thepattern defined as offsets from the first measurement position.

In an aspect, a plurality of measurements are taken across a tissue orregion and the difference between the lowest measurement value and thehighest measurement value of the plurality of measurements is recordedas a delta value of that plurality of measurements. In an aspect, 3 ormore, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more,or 10 or more measurements are taken across a tissue or region.

In an aspect, a threshold may be established for at least one region. Inan aspect, a threshold of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, orother value may be established for the at least one region. In anaspect, a delta value is identified as significant when the delta valueof a plurality of measurements taken within a region meets or exceeds athreshold associated with that region. In an aspect, each of a pluralityof regions has a different threshold. In an aspect, two or more regionsmay have a common threshold.

In an aspect, a threshold has both a delta value component and achronological component, where a delta value is identified assignificant when the delta value is greater than a predeterminednumerical value for a predetermined portion of a time interval. In anaspect, the predetermined portion of a time interval is defined as aminimum of X days where a plurality of measurements taken that dayproduces a delta value greater than or equal to the predeterminednumerical value within a total of Y contiguous days of measurement. Inan aspect, the predetermined portion of a time interval may be definedas 1, 2, 3, 4, or 5 consecutive days on which a plurality ofmeasurements taken that day produces a delta value that is greater thanor equal to the predetermined numerical value. In an aspect, thepredetermined portion of a time interval may be defined as some portionof a different specific time period (weeks, month, hours etc.).

In an aspect, a threshold has a trending aspect where changes in thedelta values of consecutive pluralities of measurements are compared toeach other. In an aspect, a trending threshold is defined as apredetermined change in delta value over a predetermined length of time,where a determination that the threshold has been met or exceeded issignificant. In an aspect, a determination of significance will cause analert to be issued. In an aspect, a trend line may be computed from aportion of the individual measurements of the consecutive pluralities ofmeasurements. In an aspect, a trend line may be computed from a portionof the delta values of the consecutive pluralities of measurements.

In an aspect, the number of measurements taken within a single regionmay be less than the number of measurement locations defined in apattern. In an aspect, a delta value will be calculated after apredetermined initial number of readings, which is less than the numberof measurement locations defined in a pattern, have been taken in aregion and after each additional reading in the same region, whereadditional readings are not taken once the delta value meets or exceedsthe threshold associated with that region.

In an aspect, the number of measurements taken within a single regionmay exceed the number of measurement locations defined in a pattern. Inan aspect, a delta value will be calculated after each additionalreading.

In an aspect, a quality metric may be generated for each plurality ofmeasurements. In an aspect, this quality metric is chosen to assess therepeatability of the measurements. In an aspect, this quality metric ischosen to assess the skill of the clinician that took the measurements.In an aspect, the quality metric may include one or more statisticalparameters, for example an average, a mean, or a standard deviation. Inan aspect, the quality metric may include one or more of a comparison ofindividual measurements to a predefined range. In an aspect, the qualitymetric may include comparison of the individual measurements to apattern of values, for example comparison of the measurement values atpredefined locations to ranges associated with each predefined location.In an aspect, the quality metric may include determination of whichmeasurements are made over healthy tissue and one or more evaluations ofconsistency within this subset of “healthy” measurements, for example arange, a standard deviation, or other parameter.

In one aspect, a measurement, for example, a threshold value, isdetermined by SEM Scanner Model 200 (Bruin Biometrics, LLC, Los Angeles,Calif.). In another aspect, a measurement is determined by another SEMscanner.

In an aspect, a measurement value is based on a capacitance measurementby reference to a reference device. In an aspect, a capacitancemeasurement can depend on the location and other aspects of anyelectrode in a device. Such variations can be compared to a referenceSEM device such as an SEM Scanner Model 200 (Bruin Biometrics, LLC, LosAngeles, Calif.). A person of ordinary skill in the art understands thatthe measurements set forth herein can be adjusted to accommodate adifference capacitance range by reference to a reference device.

In an aspect, a percentage in accordance with the present disclosure mayrange from 0-100%, such as 0-50%, 25-75%, 50-100%, 0-10%, 5-15%, 10-20%,15-25%, 20-30%, 25-35%, 30-40%, 35%-45%, 40-50%, 0-25%, 15-35%, 25-50%,45-55%, 50-60%, 55-65%, 60-70%, 65-75%, 40-55%, 50-75%, 70-80%, 75%-85%,80-90%, 85-95%, 90-100%, 65-85%, or 75-100%. In one aspect, a percentagein accordance with the present disclosure may be about 0%, 1%, 2%, 3%,4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%,55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%.

In an aspect, point 640 on curve 610 indicates a transition from zone530, where edema has occurred, to zone 520, where the tissue has amoisture content below normal. In one aspect, a measured SEM value thatequals the normal value of reference line 612 indicates that a portionof a sensor is over tissue having a higher-than-normal moisture contentwhile the remaining portion of the sensor is over tissue having alower-than-normal moisture content. In an aspect, point 640 on line A-Ais approximately the location of the edge of zone 520. If it isdesirable to excise the necrotic tissue from a patient, marking the skinat this point provides a reference to the surgeon of the edge ofnecrotic tissue.

In one aspect, successive measurements of SEM values at one or morepoints proximate to an open wound 510, for example at 30 minuteintervals for the first 4 hours, can provide information regarding thedegree of damage to the tissue. In an aspect, successive measurementscan be performed at approximately 5 minute intervals, 10 minuteintervals, 15 minute intervals, 20 minute intervals, 25 minuteintervals, 35 minute intervals, 40 minute intervals, 45 minuteintervals, 50 minute intervals, 60 minute intervals, 90 minuteintervals, or 120 minute intervals. In one aspect, successivemeasurement can be performed at time intervals for the first 1 hour, 2hours, 3 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours,11 hours, or 12 hours after an injury. In an aspect, the value andposition of point 622 over the first 4 hours post-injury may indicatethe depth of the burn and the risk of tissue depth in certain areas.Outward progression of the peak SEM values on the x-axis may indicatethe severity of the reperfusion damage.

In one aspect, measurements of SEM values may be taken with asingle-sensor device, such as a SEM scanner 170 of FIG. 1B, and logged,plotted, and assessed.

Other types of wounds, for example a cut, may suffer from zones oftissue death proximate to open wound 510. As the level of edema is stillan indication of tissue viability, the same sensing and categorizationmethod will provide valuable information to a clinician treating theinjury. Thus, the methods and apparatus described for the example burnmay also be applicable to other types of injury.

The methods and apparatus disclosed herein may also be used to track thehealing process of injuries such as burns, cuts, ulcers, and other typesof tissue damage. Closure of the skin over a wound is not the end of thehealing process, and it may take a year after the skin closes for thesub-epidermal tissue to return to its original state. Periodicassessment of the site of the original wound will show whether thehealing is continuing to progress or has halted or reversed. As anexample, pressure ulcers are known to suffer a high incidence ofrecurrence at the same location as a first ulcer. This is thought to bea result of continued pressure at the site combined with a weakenedtissue structure as a result of incomplete healing. In the absence ofcontinued measurement of the tissue state, for example with a SEMscanner, it is likely that a caregiver would consider a closed wound asa healed wound and not continue the therapy that would prevent therecurrence. Measurements of surrounding tissue at sites away from theoriginal wound can serve as a reference of what “normal” tissuemeasurements. The trend of changes, or lack thereof, of measurements atthe former wound site against this reference provides a continuedassurance that the tissue is moving toward a fully healed condition.

This monitoring of tissue improvement after the wound has healed is alsouseful to monitor the performance and efficacy of wound-healingtherapies. As an example, an electro-stimulus device may be used once awound has closed in order to accelerate the healing process of theunderlying tissue. The progress of the healing is likely to be difficultif not impossible to assess manually or visually. A SEM scanning devicecould be used to establish one or more of a SEM measurement at the siteof the closed wound, periodic measurements and trend analysis to verifythe effectiveness of the healing device, and measurement of adjacenttissue as a reference of fully healed tissue. In certain embodiments,adjustments may be made to the healing device, for example a change inthe frequency or voltage of an electro-stimulus device, based on themeasurements or the trend of the measurements made by an SEM scanner. Incertain embodiments, the use of a healing device or therapy may behalted or replaced with a different device or therapy based on the SEMmeasurements or trend. In certain embodiments, the wound may be judgedto be “healed” based on the SEM measurement and healing therapies may behalted, modified, or replaced with preventative therapies. In certainembodiments, the difference between a current SEM reading at the site ofthe wound and a reference value from nearby healthy tissue is a metricof the degree of recovery of the tissue at the wound site, where a zerodifference is fully healed and restored to original condition.

FIG. 7 depicts an aspect of a SEM sensing apparatus 700, according tothe present disclosure. In one aspect, a flexible substrate 710 has aplurality of SEM sensors 720 arranged on a common surface of substrate710. In an aspect, sensors 720 comprise toroidal sensors 90 as shown inFIG. 1A. In one aspect, sensors 720 comprise an electrode array 290 asshown in FIG. 2. In an aspect, sensors 720 comprise an electrode array400 as shown in FIG. 3. In one aspect, sensors 720 are coupled toelectronics (not shown in FIG. 7) that provide excitation and measure anSEM value of the tissue below the respective sensors 720.

In an aspect, SEM sensing apparatus 700 comprises visual indicators 730that are arranged on a substrate 710. In one aspect, visual indicators730 are on a first surface of a substrate 710 while sensors 720 are on asecond surface of substrate 710 that is opposite the first surface. Inan aspect, visual indicators 730 are disposed between at least somepairs of sensors 720. In one aspect, visual indicators 730 may be lightemitting devices (LEDs). In an aspect, visual indicators 730 may emit asingle color of light. In an aspect, visual indicators 730 mayselectably emit one of a plurality of colors of light. In one aspect,visual indicators 730 are selectable to be on or off. In an aspect,visual indicators 730 are coupled to electronics (not shown in FIG. 7)that provide excitation and selectable control of visual indicators 730.

In an aspect, electronics of the present disclosure actuate each visualindicator 730 with a color of light selected based on the SEM valuesmeasured by sensors 90 disposed on each side of the respective visualindicator 730. This provides a color-coded map of the various zones 520,530, and 540 for a given wound 500.

In one aspect, visual indicators 730 may be disposed on the same surfaceof substrate 710 as sensors 720. In an aspect, visual indicators 730comprise marking element (not visible in FIG. 7) that can selectablymark the skin of a patient on which a SEM sensing apparatus 700 isplaced. In an aspect, electronics of the present disclosure can actuatethe marking element of visual indicators 720 that are disposed along oneor more of the boundaries between zones of FIGS. 5A and 5B. In oneaspect, electronics of the present disclosure may actuate the markingelements to mark the boundary between zone 520 and zone 530, indicatingthe outer edge of non-viable tissue.

FIGS. 8A and 8B disclose an aspect of a SEM sensing assembly 702,according to the present disclosure. In one aspect, an array 740 ofelectrodes 742 is disposed on a substrate 712. In an aspect, electrodes742 are similar to electrodes 300 of FIG. 2. In one aspect, electrodes742 are similar to electrodes 410 of FIG. 3.

In an aspect, a SEM sensing apparatus 702 comprises a plurality ofperforations 750. In one aspect, perforations 750 are disposed betweenpairs of electrodes 742, as shown in FIG. 8B. In use, SEM sensingapparatus 702 can be placed on the skin of a patient over a wound and aclinician marks the skin of the patient as guided by the SEM valuesmeasured between various pairs of electrodes 742.

In an aspect, a SEM sensing apparatus 700 may comprise both visualindicators 730 and perforations 750, allowing a clinician to mark theskin of a patient as guided by the colors of various visual indicators730.

FIG. 9 discloses an aspect of an apparatus 800 for mapping areas ofdamage around a wound, according to the present disclosure. In oneaspect, a patient's arm 20 has a burn 501 with an open wound 511. In anaspect, apparatus 800 comprises an instrument head 810 overhanging arm20 with an optical system 815 that comprises a camera (not visible inFIG. 9) that observes area 825 on arm 20 and a projector (not visible inFIG. 9) that can project one or more images onto area 825, whichencompasses wound 511 as well as tissue around wound 511. In one aspect,a SEM sensing apparatus 840 is coupled to electronics (not shown in FIG.9) that also control optical system 815. In an aspect, SEM sensingapparatus 840 is coupled to electronics of the present disclosurethrough a cable 845. In an aspect, SEM sensing apparatus 840 comprises awireless linkage in place of cable 845. In one aspect, SEM sensingapparatus 840 comprises a fiducial 850 that is visible to a camera whileapparatus 800 is in use. In an aspect, SEM sensing apparatus 840comprises a single bioimpedance sensor and, therefore, measures the ECFat a single point at a time.

In use, a user can make multiple measurements with a SEM sensingapparatus 840 in area 825. At the time of each measurement, a camera canobserve and record the position of fiducial 850 in its field of view. Inan aspect, reference marks (not shown in FIG. 9) may be made on arm 20to record the position of arm 20 in the field of view and enablemovement of arm 20 during an assessment. As the set of measurementsincreases, electronics of the present disclosure determines the locationof a boundary between tissue types, for example a boundary betweenviable and non-viable tissue, and causes the projector to projectindicating images along this boundary. In FIG. 9, these images are shownas dots 710. In an aspect, a projected image may comprise lines, areasof color, areas shading from a first color to a second color, areasshading from one intensity of a color to a different intensity of thesame color, or other visual indication that provides guidance as to thecondition of the tissue in area 825.

In one aspect, electronics of the present disclosure may be coupled to aprinter (not shown in FIG. 9) and can cause the printer to produce apicture of arm 20 with wound 511 taken by a camera and overlaid withmarkings equivalent to those described as provided by a projector. In anaspect, measurements may be repeated with SEM sensing apparatus 800 andnew pictures printed, thereby creating a pictorial history of theprogression of damage around a wound. In one aspect, electronics of thepresent disclosure may be coupled to a storage device, for example aserver, and configured to store information regarding an image of arm 20and wound 511 as well as measurements and locations of the measurementsmade by a SEM sensing apparatus 840 at one or more times.

From the foregoing, it will be appreciated that the present inventioncan be embodied in various ways, which include but are not limited tothe following:

Embodiment 1. An apparatus for mapping areas of damage around a wound,the apparatus comprising: a plurality of electrodes embedded on asubstrate configured to be placed over an area of tissue that includesthe wound, where combinations of the electrodes are capable of forming aplurality of virtual capacitive sensors and each of the virtualcapacitive sensors is configured to measure a capacitance of a region oftissue proximate to the respective virtual capacitive sensor, aplurality of visual indicators embedded on the substrate, a drivecircuit electronically coupled to the electrodes and visual indicators,a processor electronically coupled to the drive circuit, and anon-transitory computer-readable medium electronically coupled to theprocessor and comprising instructions stored thereon that, when executedon the processor, perform the steps of: receiving information regardingthe measured capacitance from a subset of the plurality of virtualcapacitive sensors via the drive circuit, determining a boundary betweenviable and non-viable tissue, and activating via the drive circuit aportion of the plurality of visual indicators to indicate the boundary.

Embodiment 2. The apparatus of embodiment 1, where the substratecomprises a plurality of perforations that allow marking of the tissuealong the boundary.

Embodiment 3. The apparatus of embodiment 1, where the circuit isconfigured to selectively drive pairs of the electrodes and measure thecapacitance between each of the pairs of electrodes.

Embodiment 4. The apparatus of embodiment 3, where each of theselectively driven pairs of electrodes form one of the plurality ofvirtual capacitive sensors.

Embodiment 5. The apparatus of embodiment 1, where the circuit isconfigured to selectively drive subsets of the plurality of electrodesto form a virtual center electrode and a virtual ring electrode andmeasuring the capacitance between the virtual center electrode and thevirtual ring electrode.

Embodiment 6. The apparatus of embodiment 5, where each of the pluralityof virtual capacitive sensors comprises a virtual center electrode and avirtual ring electrode.

Embodiment 7. The apparatus of embodiment 1, where the instructionsfurther comprise the steps of: converting each measured capacitance toan associated sub-epidermal moisture (SEM) value that is associated withthe virtual capacitive sensor used to measure the capacitance, comparinga first portion of the SEM values to a first threshold, and identifyingregions of tissue corresponding to the virtual capacitive sensors thatare associated with SEM values that are greater than the first thresholdas viable.

Embodiment 8. The apparatus of embodiment 7, where the instructionsfurther comprise the steps of: comparing a second portion of the SEMvalues to a second threshold, and identifying regions of tissuecorresponding to the virtual capacitive sensors that are associated withSEM values that are less than the second threshold as non-viable.

Embodiment 9. The apparatus of embodiment 7, where each of the pluralityof visual indicators independently comprises a first mode of display anda second mode of display.

Embodiment 10. The apparatus of embodiment 9, where the instructionsfurther comprise the steps of: activating a third portion of theplurality of visual indicators in the first mode of display to indicatethe regions of tissue that are viable, and activating a fourth portionof the plurality of visual indicators in the second mode of display toindicate the regions of tissue that are non-viable.

Embodiment 11. The apparatus of embodiment 9, where: the visualindicators are light-emitting devices (LEDs), the first mode of displaycomprises emitting light having a first characteristic, and the secondmode of display comprises emitting light having a second characteristic.

Embodiment 12. The apparatus of embodiment 11, where: the firstcharacteristic comprises a first spectral content, and the secondcharacteristic comprises a second spectral content that is differentfrom the first spectral content.

Embodiment 13. An apparatus for determining a depth of a burn wound, theapparatus comprising: a pair of electrodes capable of forming acapacitive sensor that is configured to measure a capacitance of aregion of tissue proximate to the pair of electrodes, a drive circuitelectronically coupled to the capacitive sensor, a processorelectronically coupled to the drive circuit, and a non-transitorycomputer-readable medium electronically coupled to the processor andcomprising instructions stored thereon that, when executed on theprocessor, perform the steps of: receiving information regarding themeasured capacitance from the capacitive sensor via the drive circuit,comparing the information to a data array comprising pairs ofcapacitances and depths of burns, and determining the depth of the burnwound associated with the measured capacitance.

Embodiment 14. The apparatus of embodiment 13, where: the step ofreceiving information regarding the measured capacitance comprises:receiving a first capacitance measured at a first location of knownunaffected tissue, receiving a second capacitance measured at a secondlocation within the burn wound, and determining a capacitance differencebetween the first and second capacitances; the data array comprisespairs of capacitance differences and depths of burns; the step ofcomparing the information to the data array comprises comparing thecapacitive difference to the data array; and the step of determining thedepth of the burn wound comprises identifying the depth of the burnwound associated with the capacitive difference.

Embodiment 15. The apparatus of embodiment 13, where: the instructionsfurther comprise the step of converting each measured capacitance to anassociated sub-epidermal moisture (SEM) value, the data array comprisespairs of SEM values and depths of burns, the step of comparing theinformation to the data array comprises comparing the SEM value to thedata array, and the step of determining the depth of the burn woundcomprises identifying the depth of the burn wound associated with theSEM value.

Embodiment 16. An apparatus for mapping areas of damage around a wound,the apparatus comprising: a plurality of electrodes embedded on asubstrate configured to be placed over a portion of an area of tissuethat includes the wound, where pairs of the electrodes are capable offorming a capacitive sensor that is configured to measure a capacitanceof a region of tissue proximate to the capacitive sensor, a projectorcapable of projecting a visual indicator onto the area of tissue thatincludes the wound, a drive circuit electronically coupled to theplurality of electrodes and the projector, a processor electronicallycoupled to the drive circuit, and a non-transitory computer-readablemedium electronically coupled to the processor and comprisinginstructions stored thereon that, when executed on the processor,perform the steps of: receiving information regarding the measuredcapacitance from one or more of the formed capacitive sensors,determining a first boundary between a first type of tissue and a secondtype of tissue, and causing the projector to project the visualindicator to indicate the boundary.

Embodiment 17. The apparatus of embodiment 16, where the first type oftissue is a viable tissue, and the second type of tissue is a non-viabletissue.

Embodiment 18. The apparatus of embodiment 17, where the first boundaryis identified by: converting each measured capacitance to an associatedsub-epidermal moisture (SEM) value that is associated with thecapacitive sensor used to measure the capacitance, identifying regionsof tissue corresponding to the capacitive sensors that are associatedwith SEM values that are greater than a threshold as viable, identifyingregions of tissue corresponding to the capacitive sensors that areassociated with SEM values that are lesser than the threshold asnon-viable; and marking a first boundary between the viable andnon-viable regions.

Embodiment 19. The apparatus of embodiment 16, where the instructionsfurther comprise the step of determining a second boundary between thesecond type of tissue and a third type of tissue.

Embodiment 20. The apparatus of embodiment 19, where the first type oftissue is a necrotic tissue, where the second type of tissue is a tissuein a zone of stasis, and where the third type of tissue is a tissue in azone of hyperaemia.

Embodiment 21. The apparatus of embodiment 20, where the first andsecond boundaries are identified by: converting each measuredcapacitance to an associated sub-epidermal moisture (SEM) value that isassociated with the capacitive sensor used to measure the capacitance,identifying regions of tissue corresponding to the capacitive sensorsthat are associated with SEM values that are lesser than a firstthreshold as a necrotic tissue, marking the first boundary on an outeredge of the necrotic tissue regions, identifying regions of tissue in azone of stasis comprising tissue immediately surrounding the regions ofnecrotic tissue and corresponding to the capacitive sensors that areassociated with SEM values that are greater than the first threshold upto and including locations associated with a peak SEM value, and tissueimmediately surrounding the locations associated with the peak SEM valueand corresponding to the capacitive sensors that are associated with SEMvalues that are greater than a second threshold, marking the secondboundary on an outer edge of the zone of stasis; and identifying regionsof tissue in a zone of hyperaemia comprising tissue immediatelysurrounding the zone of stasis and corresponding to the capacitivesensors that are associated with SEM values that are lesser than thesecond threshold but greater than the first threshold.

Embodiment 22. A method for mapping areas of damage around a wound, themethod comprising: obtaining capacitance measurements over an area of atissue including the wound using a plurality of electrodes; convertingeach measured capacitance to an associated sub-epidermal moisture (SEM)value; and marking a first boundary encompassing regions of tissueassociated with SEM values that are lesser than a first threshold.

Embodiment 23. The method of embodiment 22, further comprising: markinga second boundary surrounding the first boundary and encompassingregions of tissues associated with SEM values that are greater than thefirst threshold up to and including locations associated with a peak SEMvalue, and tissue immediately surrounding the locations associated withthe peak SEM value and are associated with SEM values that are greaterthan a second threshold.

While the invention has been described with reference to particularaspects, it will be understood by those skilled in the art that variouschanges may be made and equivalents may be substituted for elementsthereof without departing from the scope of the invention. In addition,many modifications may be made to a particular situation or material tothe teachings of the invention without departing from the scope of theinvention. Therefore, it is intended that the invention not be limitedto the particular aspects disclosed but that the invention will includeall aspects falling within the scope and spirit of the appended claims.

1.-12. (canceled)
 13. An apparatus for determining a depth of a burnwound, said apparatus comprising: a pair of electrodes capable offorming a capacitive sensor that is configured to measure a capacitanceof a region of tissue proximate to said pair of electrodes, a drivecircuit electronically coupled to said capacitive sensor, a processorelectronically coupled to said drive circuit, and a non-transitorycomputer-readable medium electronically coupled to said processor andcomprising instructions stored thereon that, when executed on saidprocessor, perform the steps of: receiving information regarding saidmeasured capacitance from said capacitive sensor via said drive circuit,comparing said information to a data array comprising pairs ofcapacitances and depths of burns, and determining the depth of said burnwound associated with said measured capacitance.
 14. The apparatus ofclaim 13, wherein: said step of receiving information regarding saidmeasured capacitance comprises: receiving a first capacitance measuredat a first location of known unaffected tissue, receiving a secondcapacitance measured at a second location within said burn wound, anddetermining a capacitance difference between said first and secondcapacitances; said data array comprises pairs of capacitance differencesand depths of burns; said step of comparing said information to saiddata array comprises comparing said capacitive difference to said dataarray; and said step of determining the depth of said burn woundcomprises identifying the depth of said burn wound associated with saidcapacitive difference.
 15. The apparatus of claim 13, wherein: saidinstructions further comprise the step of converting each measuredcapacitance to an associated sub-epidermal moisture (SEM) value, saiddata array comprises pairs of SEM values and depths of burns, said stepof comparing said information to said data array comprises comparingsaid SEM value to said data array, and said step of determining thedepth of said burn wound comprises identifying the depth of said burnwound associated with said SEM value.
 16. An apparatus for mappingregions of damage around a wound, said apparatus comprising: a pluralityof electrodes embedded on a substrate configured to be placed over aportion of an area of tissue that includes said wound, whereincombinations of said plurality of electrodes are capable of forming aplurality of virtual capacitive sensors, each of said virtual capacitivesensors comprising at least two electrodes of said plurality ofelectrodes and configured to measure a capacitance of a region of tissueproximate to said respective virtual capacitive sensor, a projectorcapable of projecting a visual indicator onto said area of tissue thatincludes said wound, a drive circuit electronically coupled to saidplurality of electrodes and said projector, a processor electronicallycoupled to said drive circuit, and a non-transitory computer-readablemedium electronically coupled to said processor and comprisinginstructions stored thereon that, when executed on said processor,perform the steps of: receiving information regarding one or more ofsaid measured capacitance from a subset of said plurality of virtualcapacitive sensors via said drive circuit, determining a first boundarybetween a first type of tissue and a second type of tissue, and causingsaid projector to project said visual indicator to indicate saidboundary.
 17. The apparatus of claim 16, wherein said first type oftissue is a viable tissue, and said second type of tissue is anon-viable tissue.
 18. The apparatus of claim 17, wherein said firstboundary is identified by: converting each of said one or more measuredcapacitance to an associated sub-epidermal moisture (SEM) value that isassociated with each of said virtual capacitive sensors used to measuresaid capacitance, identifying regions of said viable tissuecorresponding to each of said virtual capacitive sensors that areassociated with SEM values that are greater than a threshold,identifying regions of said non-viable tissue corresponding to each ofsaid virtual capacitive sensors that are associated with SEM values thatare lesser than said threshold; and marking said first boundary betweensaid regions of viable and non-viable tissues.
 19. The apparatus ofclaim 16, wherein said instructions further comprise the step ofdetermining a second boundary between said second type of tissue and athird type of tissue.
 20. The apparatus of claim 19, wherein said firsttype of tissue is a necrotic tissue, wherein said second type of tissueis a tissue in a zone of stasis, and wherein said third type of tissueis a tissue in a zone of hyperaemia.
 21. The apparatus of claim 20,wherein said first and second boundaries are identified by: convertingeach of said one or more measured capacitance to an associatedsub-epidermal moisture (SEM) value that is associated with each of saidvirtual capacitive sensors used to measure said capacitance, identifyingregions of said necrotic tissue corresponding to each of said virtualcapacitive sensors that are associated with SEM values that are lesserthan a first threshold, marking said first boundary on an outer edge ofsaid necrotic tissue, identifying said zone of stasis comprising tissueimmediately surrounding said necrotic tissue and regions of tissuecorresponding to each of said virtual capacitive sensors that areassociated with SEM values that are greater than said first threshold upto and including regions associated with a peak SEM value, and tissueimmediately surrounding said regions associated with said peak SEM valueand regions corresponding to each of said virtual capacitive sensorsthat are associated with SEM values that are greater than a secondthreshold, marking said second boundary on an outer edge of said zone ofstasis, and identifying said zone of hyperaemia comprising tissueimmediately surrounding said zone of stasis and regions of tissuecorresponding to each of said virtual capacitive sensors that areassociated with SEM values that are lesser than said second thresholdbut greater than said first threshold.
 22. A method for mapping regionsof damage around a wound, said method comprising: obtaining one or moremeasured capacitance over an area of tissue including said wound using aplurality of electrodes; converting each of said one or more measuredcapacitance to an associated sub-epidermal moisture (SEM) value; andmarking a boundary between viable and non-viable tissue that encompassesregions of tissue associated with SEM values that are lesser than afirst threshold.
 23. The method of claim 22, further comprising: markinga second boundary surrounding said boundary, encompassing: regions oftissues associated with SEM values that are greater than said firstthreshold up to and including regions of tissues associated with a peakSEM value, and regions of tissues associated with SEM values that aregreater than a second threshold immediately surrounding said regions oftissues associated with a peak SEM value.
 24. The apparatus of claim 13,wherein said pair of electrodes comprises a center electrode surroundedby a ring electrode.
 25. The apparatus of claim 13, wherein said pair ofelectrodes comprises sets of electrodes coupled together to form virtualelectrodes.
 26. The apparatus of claim 13, wherein said pair ofelectrodes are embedded on a flexible substrate.
 27. The apparatus ofclaim 13, wherein said pair of electrodes are embedded on a rigidsubstrate.
 28. The apparatus of claim 13, wherein said instructionsfurther comprise the step of transmitting said information to a remotedevice selected from the group consisting of a computer, a tablet, amobile device, and a wearable device.